The present invention relates generally to an optical three-dimensional measurement system. More particularly, the present invention relates to a non-contact optical three dimensional measurement system using a laser structured light generator.
Many current systems exist for measuring the geometry of three-dimensional surfaces. One such system is a coordinate measurement system (CMM) which is used to measure die stamps, stamped panels, and other vehicle body structures.
The current CMM systems suffer from a variety of disadvantages. First, these CMM systems are relatively slow which limits the number of measurements that they can take during any given period of time. Second, these CMM systems require surface contact in order, to function properly, which can potentially damage the surface of the part being measured. Additionally, depending upon the geometry of the surface being measured, an instrument that needs to contact the surface to perform measuring risks damage due to contact with the surface as it moves to various surface points. These CMM systems are thus typically only used in connection with small-scale projects, which makes them relatively inefficient.
Additionally, current measurement systems typically have a variety of mechanically moving parts. These moving parts can cause vibrations in the system, which can affect the accuracy of the measurements. In order to reduce the inaccuracy and/or unreliability in the measurements of the systems that utilize mechanically moving parts, the system has to allow time for the vibration to settle before the measurements are taken. This, however, adds to the time of the process and therefore increases the cost. These systems also have limitations in data acquisition speed, size, and reliability.
U.S. Pat. No. 6,100,984, discloses a system that solves many of the above-noted problems and improves on prior measurement systems. The disclosed measurement system of the ""984 patent includes a laser which emits a beam through an objective lens, which expands the laser beam into a diverged beam. The diverged beam passes through a liquid crystal system that is located forwardly of the objective lens with respect to the laser. The liquid crystal system receives the diverged beam and generates at least one fringe pattern on a surface of a part to be measured. The liquid crystal system is in communication with a computer to control the pitch and phase of the fringe pattern.
While the system disclosed in U.S. Pat. No. 6,100,984 has been found to be extremely effective, it would be advantageous if a measurement system could be developed for measuring part surfaces or other surface geometry that was more compact, more accurate, and more efficient.
It is therefore an object of the present invention to provide a non-contact optical based three dimensional measurement system that is light in weight, compact, and accurate.
It is another object of the present invention to provide a non-contact optical based three dimensional measurement system that has high data acquisition speeds.
It is a further object of the present invention to provide a three dimensional measurement system that can decrease the cost of die development and vehicle body design.
It is still a further object of the present invention to provide a three dimensional measurement system that is insensitive to environmental vibration.
In accordance with the objects of the present invention, a measurement system for measuring the surface geometry of parts in three dimensions is provided. The measurement system includes a laser for emitting a laser beam. The laser beam is first passed through a birefringement crystal which splits the beam into two beams. The split beam then passes from the crystal to a liquid crystal system, which is in communication with a computer system. The diverged beam is then passed to a laser beam expander which expands the two laser beams and allows them to overlap or superimpose in the space to interface with each other to form fringe patterns on the surface to be measured. A camera, sensor, or other photographic equipment is positioned to take an image of or analyze the fringe pattern on the surface. Thereafter, the computer and the liquid crystal system perform a phase shift on the fringe pattern and then take another picture of another image.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.